1. Field of the Invention
The present invention relates to a flat panel display device and a method of inspection of the same, more particularly relates to a flat panel display device, an active matrix drive substrate, and methods of inspection of the same which enable the number of output terminals used for the inspection of the horizontal scanning circuit and the vertical scanning circuit formed on the drive substrate of a liquid crystal display device, for example, to be slashed and the inspection time to be shortened.
2. Description of the Related Art
A representative type of a flat panel display device is a liquid crystal device (LCD). A LCD generally is comprised of a drive substrate on which a horizontal scanning circuit, vertical scanning circuit, and a pixel region are formed, a counter substrate on which counter electrode is formed, and a liquid crystal sealed between the two. The pixel region has a plural of picture elements in a matrix array. Each picture element has a pixel electrode and a drive circuit. The drive circuits are, for example, comprised of switch elements, and are driven for each picture element selected by the horizontal scanning circuit and the vertical scanning circuit to cause an optical change in the portion of the liquid crystal corresponding to each picture element and thereby display an image.
The above-mentioned horizontal scanning circuit and vertical scanning circuit can be formed on a substrate separate from the drive substrate on which the pixel drive circuits are formed, but the trend is for formation on the same drive substrate due to the demands for greater compactness of the device etc.
In the process of production of an LCD, various inspection processes are required at each stage of the production. For example, one of these is the inspection of the operation of the horizontal scanning circuit and the vertical scanning circuit. If these circuits do not both operate normally, the finished LCD will also not operate normally.
Therefore, in the prior art, provision was made of an inspection-use output terminal for each of the horizontal scanning circuit and the vertical scanning circuit (a total of two inspection-use output terminals), these circuits were independently made to operate after the production of the drive substrate or after the assembly of the drive substrate and the counter substrate and the filling of the liquid crystal, the output waveforms were taken out from the output terminals, and the inspections were performed using the same. That is, in the conventional method of inspection, it was considered that at least two inspection-use output terminals were required for inspecting the horizontal scanning circuit and the vertical scanning circuit.
However, these two inspection-use output terminals are used only for inspection purposes and are not required at all during the normal state of usage of the LCD. There has been a demand for reduction of the unnecessary output terminals as much as possible from the viewpoint of preventing external disturbances such as static electricity.
Further, in the prior art, the horizontal scanning circuit and the vertical scanning circuit were inspected independently of each other, so there was the problem of a long time being required for the inspections.